During the development process of oil, it is needed to take out a fluid in a downhole formation to analyze properties of the fluid and make an oil well exploitation scheme.
At present, a downhole formation fluid extraction apparatus available on the market is in the mode of a hydraulic plunger pump and controls the reciprocation of a hydraulic pump by controlling the reversal of direction of the hydraulic pump using an electromagnetic valve to realize a purpose of extracting a formation fluid. The control over the reciprocation of a plunger pump of this structure depends on an electromagnetic valve which is easily polluted by oil, leading to poor reliability of overall system and relatively high maintenance cost. Besides, it is not easy to control an extraction volume and a discharge volume precisely, resulting in that the amount of a sample acquired is not precise.